FIG. 1 is cutaway view of a related art reactor pressure vessel 10, such as an ESBWR pressure vessel. Vessel 10 includes a core plate 18 laterally supporting one or more fuel assemblies 1 within core shroud 14. Core shroud 14 separates upward flow of coolant through the core and assemblies 1 therein from downward flow in downcomer annulus 4. Core plate 18 further supports core shroud 14 and may itself be supported by support ring and legs 2. Top guide 12 is positioned at a top of the core shroud 14 and potentially bolted to core shroud 14. Top guide 12 may be a grid structure that provides lateral support and positioning to the top of fuel assemblies 1. Each opening in top guide 12 can provide lateral support and guidance for four fuel assemblies 1 (or in the case of peripheral openings at the edge of the core, two or three fuel assemblies). One or more instrumentation tubes 50 and control rod drives may extend through a bottom of vessel 10 for control and monitoring of the conditions in the core.
As liquid coolant boils among assemblies 1, a heated mixture of steam and water flows upward through top guide 12. Chimney 20 receives the energetic steam/water mixture exiting fuel assemblies 1, which flows through partitions 21 in chimney 20 to limit cross flow and minimize potential for recirculating eddies in this heated coolant moving up through reactor 10. Chimney 20 supports steam separators 40 at an opposite end via chimney head 22 laterally supported by chimney restraint 23. After exiting chimney 20, the steam/water mixture is directed into steam separators 40 that separate liquid water from the steam-water mixture rising therethrough. Steam from the steam separators 40 flows upward to steam dryers 41, where additional moisture is removed. The separated and removed liquid is directed into downcomer annulus 4 between the outer wall of chimney 20 and inner wall of vessel 10. The dried steam exiting steam dryers 41 is then directed into main steam lines 3 for electrical power production.
New makeup feedwater is received from main feedwater line 11 flowing into downcomer annulus 4. The feedwater is typically heated, but still cooler than liquid water redirected from dryers 41 and steam separators 40 in downcomer annulus 4. For example, incoming feedwater from line 11 may be up to 100 or more degrees Fahrenheit cooler than temperature of water, operating near a boiling temperature, when flowing from dryers 41 and steam separators 40 into downcomer annulus 4 for recirculation through the reactor. To evenly distribute feedwater from line 11, a distribution system may be used in annulus 4 to evenly distribute new feedwater flow. FIGS. 2A and 2B are top and front views of related art feedwater sparger assemblies 24 useable to so distribute new feedwater flow. As seen in FIGS. 2A and 2B, sparger assembly 24 connects to main feedwater line 11 and distributes the water across an annular space.